1. Field of the Invention
The present invention relates generally to the problem of defoaming encountered in many industrial chemical processes. More particularly, the present invention relates to a composition for use in suppressing and controlling foam in such chemical processes. Still more particularly, the present invention relates to a defoaming composition particularly adapted for use in industrial chemical processes in which a high concentration of surfactant is employed rendering existing defoaming compositions less than acceptably effective.
2. Description of the Prior Art
Foaming is a constant problem in various industrial chemical processes such as, for example, the sulfite, sulfate and soda processes used in the pulp and paper industry for pulping wood chips, the stripping of monomers in the manufacture of synthetic elastomers and other polymeric products, the discharge of effluent streams in various industries, and the like. Numerous methods and means have been proposed for combating this problem in these and other industries where foaming occurs, including the use of various types of defoaming compositions. One class of defoaming composition that has proved to be quite successful comprises the suspension of a hydrophobic solid in a water-insoluble vehicle. U.S. Pat. No. 3,076,768, for instance discloses the use of a minor proportion of silica which has been treated with a dimethylpolysiloxane oil to render its surface hydrophobic, dispersed in a major proportion of any of various water-insoluble organic liquids such as chlorinated and non-chlorinated naphthenic and paraffinic mineral oils. U.S. Pat. No. 3,671,460 suggests similarly treating a hydrophilic alumina monohydrate with a liquid polysiloxane oil and then incorporating the resultant hydrophobic alumina in a water-insoluble vehicle such as an aliphatic, acyclic or aromatic hydrocarbon, or mixtures thereof, to form a dispersion in which the hydrophobed alumina is in a minor proportion to the hydrocarbon vehicle.
Still other defoaming compositions comprising a hydrophobic solid dispersed in a water insoluble organic liquid are disclosed in other patents. For example, in U.S. Pat. No. 3,652,453, a hydrophobic reaction product of a polyamine, such as ethylene diamine, and a fatty acid, such as stearic acid, is treated to form a melt which is then incorporated in a water insoluble organic liquid vehicle such as mineral oil, any of various alcohols, or the like. U.S. Pat. No. 3,673,105 also discloses the use of a polyamide fatty acid reaction product, such as ethylene bis-stearamide, dispersed as the hydrophobic solid in a paraffin mineral oil, or other suitable inert liquid hydrocarbon. The use of both hydrophobic silica and a bis-amide in a water insoluble organic liquid such as silicone oil or in an aqueous medium are shown in U.S. Pat. Nos. 3,923,683 and 4,107,073. Numerous other patents show various modifications to these several types of defoaming compositions.
Another class of defoaming composition that has enjoyed considerable success is a solid mixture comprising a linear alcohol of high carbon content, a saturated fatty acid, and a fatty acid soap in which the alcohol and acid are hydrophobic, such as disclosed in Canadian Pat. No. 534,604. Because it is desirable in many situations to have a free flowing composition that can be pumped directly from its place of storage to the point of application, it was proposed to form an aqueous dispersion of the composition as disclosed in U.S. Pat. No. 4,340,500. In the preparation of an aqueous defoaming composition of this type, a surfactant is employed to emulsify the alcohol and fatty acid in the water at temperatures above their melting points. The soap can be prepared in situ, if desired, from a portion of the fatty acid content by incorporating a suitable soap forming amine after the emulsion has been cooled. A further modification of this free flowing aqueous defoaming composition containing hydrophobic alcohol and fatty acid components is disclosed in U.S. Pat. No. 4,303,549 which teaches the introduction of a suitable water soluble metal salt e.g., alum, into the dispersion to provide hydrophobic particle surfaces.
While these aqueous free flowing alcohol-fatty acid-soap defoaming compositions have proved to be quite successful in commercial application, they have a drawback in that their effectiveness decreases markedly as the surfactant concentration of the system being treated increases. Accordingly, ever increasing quantities of defoaming composition, disproportionate with respect to what might be expected for the degree of increase in the surfactant concentration of the system being treated, must be employed as the surfactant concentration increases in order to obtain an acceptable level of foam suppression and control. Accordingly, not only does it become more difficult to control foam under conditions of high surfactant concentration, it also becomes, at the same time, economically more unattractive.